1. Field of the Invention
This invention relates to the field of data processing, and, more particularly, to an improved non-volatile parallel-to-serial converter having amorphous silicon thin-film floating-gate transistors that non-volatilely store data in the event power is turned off or lost.
2. Description of Related Art
Amorphous thin-film transistors provide a technology that is advantageous for large area, low cost integrated circuits. One type of such transistors has a floating gate that can be used to provide non-volatile storage of data. There are many different devices commonly used in digital circuits which temporarily store data and wherein the data is lost when power is turned off and in the event of a power failure. A parallel-to-serial converter is an example of such a device. The invention is directed to an improved parallel-to-serial converter in which amorphous silicon thin-film floating-gate transistors are used to buffer or temporarily store data while power is turned on and to non-volatilely store data in the event power is lost or turned off. Such preservation of the data may advantageously be used for diagnostic, start-up, and resume operations.
It is recognized that floating gate transistors have been implemented using crystalline semiconductor material. Such transistors are operated by injecting a charge onto the floating gate by means of an avalanche breakdown of the insulator surrounding the floating gate. Such transistors find use in erasable programmable read only memories (EPROM) where the injected charge can be non-volatilely stored for long periods of time when power is off. However, a crystalline floating gate transistor has limited uses since it requires a relatively long period of time to erase the charge and reprogram the transistor, and the insulator has a limited life due to the deleterious effect of the avalanche breakdown.